It is well known that prolonged exposure to ultraviolet (UV) radiation, especially from the sun, can lead to the formation of light dermatoses and erythemas, and increase the risk of skin cancers, such as melanoma. Exposure to UV radiation also accelerates skin aging, such as loss of skin elasticity and wrinkling.
For these reasons, sunscreen compositions are commonly used to provide photoprotection from the sun. Sunscreen compositions containing inorganic sunscreen agents, i.e., metal oxides like zinc oxide or titanium dioxide, are preferred by many consumers who desire mild products with a minimum of potentially irritating ingredients. Metal oxides, however, are difficult to formulate into sprayable compositions, a product form that is popular due to convenient application. As dense particles, metal oxides tend to settle in formulations, and are therefore difficult to suspend in dispersions over extended time periods, e.g. product shelf life. This is especially true for sunscreen compositions having little or no organic UV filter content, which require higher loads of metal oxides for adequate UV protection.
It has now been discovered that a composition comprising high levels of metal oxides that is both sprayable and stable may be prepared using a combination of a branched hydrophobically modified ethoxylated urethane copolymer (“HEUR”) and a hydrophobically modified alkali swellable (“HASE”) emulsion copolymer. Advantageously, the composition may be a sunscreen, and in certain embodiments is substantially free or completely free of organic UV filters.